Compounds, compositions and methods to reduce SOx emissions from FCC units

ABSTRACT

Anionic clay compounds such as hydrotalcite-like compounds can be made by a process wherein a non-hydrotalcite-like compound (or a hydrotalcite-like compound) are heat treated and then hydrated to form hydrotalcite-like compounds having properties (e.g.., increased hardness and/or density) that differ from those of hydrotalcite-like compounds made by prior art methods wherein non-hydrotalcite-like compounds (or hydrotalcite-like compounds) are not similarly heat treated and hydrated to form such hydrotalcite-like compounds.

RELATED APPLICATIONS

[0001] This is a Continuation of Application No. 10/290,012 filed Nov.7, 2002, which is a Continuation of Application No. 09/457,802 filedDec. 9, 1999, issued as U.S. Pat. No. 6,479,421, which is a divisionalof Application No. 08/955,017, filed Oct. 20, 1997, issued as U.S. Pat.No. 6,028,023.

BACKGROUND OF THE INVENTION

[0002] This invention is generally concerned with methods of makinganionic clays. Such clays are characterized by crystalline structuresthat consist of positively charged layers that are separated byinterstitial anions and/or water molecules. The positively chargedlayers are often comprised of metal hydroxides of divalent metal cations(e.g., Mg²⁺, Ca²⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Sr²⁺, Ba²⁺ and Cu²⁺) andtrivalent metal cations (e.g., Al³⁺, Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺, Cr³⁺, Ga³⁺,B³⁺, La³⁺ and Gl³⁺). The interstitial anions are usually NO₃—, OH—, Cl—,Cr—, I—, CO₃ ²⁻, SO₄ ²⁻, SIO₃ ²⁻, HPO₃ ²⁻, MnO₄—, HGaO₃ ²⁻, HVO₄ ²⁻,CIO₄—, BO₃ ²⁻, monocarboxylate (e.g., acetate) and dicarboxylates (e.g.,oxalate), alkyl sulphonates (e.g., lauryl sulphonate) and variouscombinations thereof.

[0003] Therefore, anionic clays are further subdivided according to theidentity of the atoms that make up their crystalline structures. Forexample, anionic clays in the pyroaurite-sjogrenite-hydrotalcite groupare based upon brucite-like layers (wherein magnesium cations areoctahedrally surrounded by hydroxyl groups) which alternate withinterstitial layers of water molecules and/or various anions (e.g.,carbonate ions). When some of the magnesium in a brucite-like layer isisomorphously replaced by a higher charged cation, e.g., Al³⁺, then theresulting Mg²⁺—Al³⁺—OH layer gains in positive charge. Hence, anappropriate number of interstitial anions, such as those noted above,are needed to render the overall compound electrically neutral.

[0004] The literature also teaches that as the concentration of Al³⁺increases in a Brucite-type lattice, a reduction of the latticeparameter known as “a”, takes place. The lattice parameter known as “c”also is reduced. The reduction in lattice parameter, a, is due to thesmaller, plus three charged, Al³⁺ ions substituting for the larger, plustwo charged Mg²⁺ ions. This higher charge causes increased coulombicforces of attraction between the positive charged Brucite-type layer andthe negative interlayer ions—thus giving rise to a decrease in the sizeof the interlayer itself.

[0005] Natural minerals that exhibit such crystalline structuresinclude, but by no means are limited to, pyroaurite, sjogrenite,hydrotalcite, stichtite, reevesite, eardleyite, mannaseite, barbertoniteand hydrocalumite. The chemical formulas for some of the more commonsynthetic forms of anionic clays would include: [Mg₆Fe₂(OH)₁₆]CO₃.4H₂O,[Mg₆Al₂-(OH)₁₆]CO₃. 4H₂O, [Mg₆Cr₂(OH)₁₆]CO₃.4H₂O,[Ni₆-Fe₂(OH)₁₆]CO₃.4H₂O, [Ni₆Al₂(OH)₁₆]CO₃.4H₂O, [Fe₄Fe₂(OH)₁₂]CO₃.#H₂O,[Ca₂Al(OH)₆](OH)_(0.75)-(CO₃)_(0.125). 2.5H₂O₆]OH.6H₂O,[Ca₂Al—(OH)₆]OH.3H₂O, [Ca₂Al(OH)₆]OH.2h₂O, [Ca₂Al—(OH)₆]OH,[Ca₂Al(OH)₆]Cl.2H₂O, [Ca₂Al(OH)₆]0.5CO₃.2.5H₂O, [Ca₂Al(OH)₆]0.5SO₄.3H₂O,[Ca₂—Fe(OH)₆]0.5SO₄3H₂O, [(Ni, Zn)₆Al₂(OH)₁₆]CO₃4H₂O, [Mg₆(Ni,Fe)₂(OH)₁₆](OH)₂.2H₂O, [Mg₆Al₂(OH)₁₆-](OH)₂.4H₂O,[(Mg₃Zn₃)al₂(OH)₁₆]CO₃4H₂O, [Mg₆Al₂(OH)₁₆]SO₄.xH₂O,[Mg₆Al₂(OH)₁₆](NO₃.x—H₂O, [Zn₆Al₂(OH)₁₆]CO₃.xH₂O,[Cu₆Al₂(OH)¹⁶⁻]CO₃.xH₂O, [Cu₆Al₂(OH)₁₆]SO₄.xH₂O and[Mn₆Al²⁻(OH)₁₆]CO₃.xH₂O, wherein x has a value of from 1 to 6.

[0006] Those skilled in this art also will appreciate that anionic claysare often referred to as “mixed metal hydroxides.” This expressionderives from the fact that, as noted above, positively charged metalhydroxide sheets of anionic clays may contain two metal cations indifferent oxidation states (e.g., Mg²⁺ and Al⁺). Moreover, because theXRD patterns for so many anionic clays are similar to that of themineral known as Hydrotalcite, Mg₆Al₂(OH)₁₆(CO₃).4H₂O, anionic claysalso are very commonly referred to as “hydrotalcite-like compounds.”This term has been widely used throughout the literature for many years(see for example: Pausch, “Synthesis of Disordered and Al-RichHydrotalcite-Like Compounds,” Clay and Clay Minerals, Vol. 14, No. 5,507-510 (1986). Such compounds also are often referred to as “anionicclays.” Indeed, the expressions “anionic clay,” “mixed metal hydroxides”and “hydrotalcite-like compounds” are often found very closely linkedtogether. For example, in: Reichle, “Synthesis of Anionic Clay Minerals(Mixed Metal Hydroxides, Hydrotalcite),” Solid State Ionics, 22, 135-141(1986) (at Paragraph 1, page 135) the author states: “The anionic claysare also called mixed metal hydroxides since the positively chargedmetal hydroxide sheets must contain two metals in different oxidationstates. Crystallographically they have diffraction patterns which arevery similar or identical to that of hydrotalcite(Mg₆Al₂(OH)₁₆(CO₃).4H₂O); hence they have also been referred to ashydrotalcites or hydrotaicite-like.” (emphasis added). U.S. Pat. No.5,399,329 (see col.1, lines 60-63) contains the statement: “The term‘hydrotalcite-like’ is recognized in this art. It is defined and used ina manner consistent with usage herein in the comprehensive literaturesurvey of the above-referenced Cavani et al. article.” Hence, for thepurposes of the present patent disclosure, applicant will (unlessotherwise stated) use the term “hydrotalcite-like” compound(s) with theunderstanding that this term should be taken to include anionic clays,hydrotalcite itself as well as any member of that class of materialsgenerally known as “hydrotalcite-like compounds.” Moreover, because ofits frequent use herein, applicant will often abbreviate the term“hydrotalcite-like” with “HTL.”

[0007] The methods by which HTL compounds have been made are foundthroughout the academic and the patent literature. For example, suchmethods have been reviewed by Reichle, “Synthesis of Anionic ClayMinerals (Mixed Metal Hydroxides, Hydrotalcite),” Solid States Ionics,22 (1986), 135-141, and by Cavani et al., CATALYSTS TODAY, Vol. 11, No.2, (1991). In the case of hydrotalcite-like compounds, the most commonlyused production methods usually involve use of concentrated solutions ofmagnesium and aluminum which are often reacted with each other throughuse of strong reagents such as sodium hydroxide, and various acetatesand carbonates. Such chemical reactions produce hydrotalcite orhydrotalcite-like compounds which are then filtered, washed, and dried.The resulting HTL compounds have been used in many ways—but their use ashydrocarbon cracking catalysts, sorbents, binder materials for catalystsand water softener agents is of particular relevance to this patentdisclosure.

[0008] It also is well known that HTL compounds will decompose in apredictable manner upon heating and that, if the heating does not exceedcertain hereinafter more fully discussed temperatures, the resultingdecomposed materials can be rehydrated (and, optionally, resupplied withvarious anions, e.g., C₃ ^(═), that were driven off by the heatingprocess) and thereby reproduce the original, or a very similar, HTLcompound. The decomposition products of such heating are often referredto as “collapsed,” or “metastable,” hydrotalcite-like compounds. If,however, these collapsed or metastable materials are heated beyondcertain temperatures (e.g., 900° C.), then the resulting decompositionproducts of such hydrotalcite-like compounds can no longer be rehydratedand, hence, are no longer capable of forming the originalhydrotalcite-like compound.

[0009] Such thermal decomposition of hydrotalcite-like compounds hasbeen carefully studied and fully described in the academic and patentliterature. For example, Miyata, “Physico-Chemical Properties ofSynthetic Hydrotalcites in Relation to composition,” Clays and ClayMinerals, Vol. 28, No. 1, 50-56 (1980), describes the temperaturerelationships and chemical identity of the thermal decompositionproducts of hydrotalcite in the face of a rising temperature regime inthe following terms:

[0010] “It is of interest to know the form in which the Al occurs afterthermal decomposition of the hydrotalcite structure. A sample withx=0.287, hydrothermally treated at 200° C. for 24 hr, was calcined at300°-1000° C. in air for 2 hr. After calcination at 300° C., bothhydrotalcite and MgO were detected by X-ray diffraction, but aftercalcination at 400°-800° C. only MgO could be detected. At 900° C. MgO,MgAl₂O₄, and a trace of γ—Al₂O₃ were detected.” (emphasis added, forreasons to be explained in the ensuing portions of this patentdisclosure)

[0011] Miyata then goes on to note that:

[0012] “The crystallite size was smaller than so A when the sample wascalcined below 800° C. This value was much smaller than that for MgOobtained from pure Mg(OH)₂. On calcination above 800° C., thecrystallite size rapidly increased. The changes of the crystallite sizeand lattice parameter a have the same tendency. Consequently, Alsubstituting in MgO acts to inhibit crystal growth. If Al-containing MgOis reacted with water, it should first form hydrotalcite. Hydrotalcitecalcined at 400°-800° C. with x =0.287 was hydrated at 80° C. for 24 hr,and the products were examined by X-ray powder diffraction. According toTable 7, hydrotalcite was the only hydrated product detected in samplescalcined at 400°-700° C. The lattice parameter a is the same as that ofthe original sample. The samples calcined at 800° C. also formed onlyhydrotalcite but their lattice parameters are larger than that of theoriginal sample. According to FIG. 1, the molar ratio of this product isx=0.235. On the other hand, Al₂O₃ does not react with water under theabove-mentioned conditions. Therefore, the results suggest that Alenters product MgO when hydrotalcite is calcined between 400 and 700°C.” (emphasis added)

[0013] U.S. Pat. No. 5,459,118 (“the '118 patent”) describes thecharacter of the materials that result from progressively heatinghydrotalcite-like compositions (HTlc's) in a passage running from col.4, line 67 to col. 5, line 14. It reads as follows:

[0014] “The natural products of calcination or activation in inert gasof a HTlc is believed to be a spinel. In the range between thetemperature at which HTlc decomposition commences (between 572° and 752°F.) (i.e., between 300° C. and 400° C.) and that of spinel formation(1652° F.) (i.e., at 900° C.), a series of metastable phases form, bothcrystalline and amorphous. Therefore, the surface area, pore volume, andstructure depend on the temperature of calcination. Upon calcination,the crystal structure of DHT-4A is decomposed at about 660° F. (i.e.,349° C.) when water and carbon dioxide evolved from the structure, and aMgO—Al₂O₃ solid solution of formula 4.5 MgO.Al₂O₃ is formed. This solidsolution is stable up to 1472° F. (i.e., 800° C.) MgO and MgAl₂O₄ areformed at about 652° F. (i.e., 900° C.). On the other hand, the solidsolution calcined at less than 1472° F. (i.e., 800° C.) can be restoredin the original structure by hydration.” (The underlined portions ofthis passage have been added to convert °F. to °C. in order to moredirectly compare the teachings of this reference with other relevantreferences wherein temperatures are expressed in °C., again suchcomparisons will be made in the next few paragraphs of this patentdisclosure)

[0015] It might also be noted here that this quotation from the '118patent is a precise statement of the temperatures at which certainhydrotalcite decomposition products are described (e.g., spinel,MgAl₂O₄, formation taking place at 900° C. when hydrotalcite isthermally decomposed). This more exact knowledge of the temperatures atwhich certain aspects of the decomposition of hydrotalcite take place,clarifies many other, more general, statements found in the literatureconcerning the temperatures at which certain decomposition products areformed (e.g., statements concerned with the temperature at which spinel,MgAl₂O₄, is formed from a hydrotalcite starting material). That is tosay that many, more general, statements concerning the temperatures atwhich various hydrotalcite thermal decomposition products (e.g., spinel,MgAl₂O₄) are formed must be carefully interpreted. For example, in U.S.Pat. No. 4,889,615 (“the '615 patent”) at col. 6, lines 36-43, we findthe statement:

[0016] “Calcining the Mg/Al hydrotalcites at temperatures greater than5000° C. gives a mixture of MgO and MgAl₂O₄, a magnesium aluminatespinel, a material which has been reported to reduce FCC regeneratorSO_(X) emissions (see U.S. Pat. Nos. 4,469,589 (Yoo) and 4,472,267(Yoo)). The activity of the dehydrated hydrotalcite is, however,significantly different than that observed for the spinel, MgO, ormixtures of both. No evidence of MgAl381₂O₄ (sic) is observed in theregenerated hydrotalcite indicating that the spinel is not the activecomponent.” (emphasis added)

[0017] Thus, in view of the previous, more precise, descriptions of thetemperature of spinel formation (i.e., 900° C.) in the '118 patent, itseems that the more general expression “temperatures greater than 500°C.” used in the '615 patent should not be taken to mean something like501° C., but rather should be taken to mean 900° C., a temperature whichis indeed “greater than 500° C.” It also should be noted that theabove-quoted passage recognizes that “spinel is not the activecomponent” of the materials described in the '615. We note this pointhere because it is consistent with applicant's hereinafter describedgoal of not making spinel—so that applicant's heat treated, intermediateproducts can in fact be hydrated (or rehydrated) to formhydrotalcite-like compositions.

[0018] A similar general statement concerning spinel formation from ahydrotalcite precursor appears in U.S. Pat. No. 4,458,026. There (atcol. 3, lines 54-56) we find the statement:

[0019] “Above 600° C. the resulting metal oxide mixture begins to sinterand lose surface area, pore volume, as well as form a catalyticallyinactive phase (spinel—MgAl₂O₄.” (emphasis added)

[0020] Here again, applicant is of the opinion that the generalexpression “Above 600° C.” should not be taken to mean something like601° C., but rather should be taken to mean fair enough above 600° C. toform spinel—MgAl₂O₄ that is to say 900° C., the temperature at whichspinel formation from a hydrotalcite-like compound has been moreprecisely determined. This quotation also notes that spinel is“catalytically inactive”.

[0021] Indeed, one can even find generalized statements about thetemperature of spinel formation that are better interpreted to meanlower temperature levels. For example, in U.S. Pat. No. 5,114,898 (atcol. 4, lines 43-51) we find the statement:

[0022] “Reichle in J. Catal. 101, 352 to 359 (1986) has shown that thisheating of hydrotalcite was accompanied by an increase in the surfacearea from about 120 to about 230 m²/g (N₂/BET) and a doubling of porevolume (0.6 to 1.0 cm³/g, Hg intrusion). Further heating to highertemperatures causes lowering of surface area as well as reactivity. At1000° C., the formation of MgO and the spinel phase, MgAl₂O₄ has beenobserved.” (emphasis added)

[0023] In this case, applicant thinks that the statement “At 1000° C.the formation of MgO and spinel phase has been observed”, is bettertaken to mean: spinel is observed at 1000° C. because spinel (MgAl₂O₄)forms at 900° C.—rather than taken to mean: 1000° C. is the temperatureof formation of spinel. Indeed, applicant has by his own experimentalwork confirmed that spinel begins to from in HTL compounds at 9000° C.

[0024] The prior art also has noted that when various anionicclay-forming ingredients such as hydrotalcite-forming ingredients (e.g.,magnesium-containing compositions and aluminum-containing compositions)are mixed under certain prescribed conditions (e.g., certain agingtimes, pH conditions, temperatures, etc.), the resulting slurry orprecipitate materials (e.g., hydrotalcite-like materials) will exhibitdistinct catalytic properties. Hence, many such production processes arebased upon fine tuning of such time, temperature, pH, etc. conditions inorder to obtain maximum amounts of a given kind of hydrotalcite-likeprecipitate product.

[0025] The slurry and/or precipitate products of such initial chemicalreactions also have been heat treated to obtain various “collapsed” or“metastable” hydrotalcite materials that have specific catalyticproperties. Such collapsed materials have, for example, been used assorbents (and especially Sox sorbents for fluid catalytic and fixedhydrocarbon cracking processes), hydrocarbon cracking catalysts,catalyst binders, anion exchangers, acid residue scavengers andstabilizers for polymers, and even as antacids intended for use in thecontext of human medicine.

[0026] The prior art also has long recognized that other ingredientssuch as compounds containing Ce, V, Fe and Pt can he added to theoriginal hydrotalcite-forming reaction mixtures so they will appear as adistinct phase of various solid products created by such reactions.Dried forms of such anionic clays (e.g., microspheroidal particles ofsuch hydrotalcite-like compounds used as So_(x) sorbents in fluidcatalytic conversion (FCC) processes) also have been impregnated withsolutions of such metals. Moreover, such metals have even been made aintegral part of the crystalline structure of hydrotalcite-likematerials (see, for example, U.S. Pat. No. 5,114,691 and U.S. Pat. No.5,114,898 which teach use of sulfur oxidizing catalysts made of layereddouble hydroxide (LDH) sorbents, e.g., hydrotalcite-like materials thatcontain metal ions (e.g., those of vanadium) that replace some or all ofthe divalent metals (Mg²⁺) or trivalent metals (Al³⁺) that form thelayers of the LDH).

[0027] Hydrotalcite-like compounds that are used as catalysts also havebeen both heat treated and associated with various catalyst binder ormatrix materials. For example, U.S. Pat. No. 4,866,019 (the '019 patent)discloses that hydrotalcite can be heat treated and used in associationwith various binder materials. U.S. Pat. No. 5,153,156 teaches a methodfor making magnesium/aluminum synthetic anionic clay catalysts by (1)spray drying a slurry of a magnesium aluminum synthetic clay, (2) makinga plasticized mixture of the spray dried clay with diatomaceous earthand (3) forming, drying and calcining the resulting plasticized mixture.

[0028] The prior art also has long recognized that anionic claymaterials can be used to catalyze certain specific chemical reactions.For example, U.S. Pat. No. 4,458,026 teaches use of certain heat treatedanionic clay materials as catalysts for converting acetone to mesityloxide and isophorone. The anionic clays are given this catalyticactivity by heating them to temperatures ranging from about 300 to 600°C.

[0029] U.S. Pat. No. 4,952,382 teaches a hydrocarbon conversion processthat employs a catalyst composition containing an anionic clay whereinthe anionic clay serves as a sulfur oxides binding material.

[0030] U.S. Pat. No. 4,970,191 teaches use of polymorphicmagnesium-aluminum oxide compositions as catalysts in various basecatalyzed reactions such as alcohol condensation, isomerization ofolefins, etc.

[0031] U.S. Pat. No. 4,889,615 discloses a vanadium trap catalystadditive comprising a dehydrated magnesium-aluminum hydrotalcite.

[0032] U.S. Pat. No. 5,358,701 teaches the use of layered doublehydroxide (LDH) sorbents such as hydrotalcite-like materials as SO₂sorption agents. This reference postulates that the sulfur-containinggas absorbs into the hydrotalcite structure as SO₃ ²⁻ anions byreplacing the gallery CO₃ ²⁻ anions. The absorbed sulfur is thereafterdriven off by calcination at elevated temperatures (500° C.). The LDHsorbents are regenerated by hydrolyzing the calcined product,particularly in the presence of CO₂ or CO₃ ²⁻.

[0033] U.S. Pat. No. 5,114,691 teaches removing sulfur oxide from gasstreams using heated layered double hydroxide (LDH) sorbents havingmetal-containing: oxoanions incorporated into the galleries of the LDHstructures.

[0034] U.S. Pat. No. 4,465,779 teaches catalytic cracking compositioncomprising a solid, cracking catalyst and a diluent containing amagnesium compound in combination with a heat-stable metal compound.

[0035] U.S. Pat. No. 5,426,083 teaches catalytic use of a collapsedcomposition of microcrystallites comprised of divalent metal ions,trivalent ions, vanadium, tungsten or molybdenum.

[0036] U.S. Pat. No. 5,399,329 teaches making hydrotalcite-likematerials by preparing a mixture of magnesium (divalent cation) toaluminum (trivalent cation) in a molar ratio between 1.1 and 10:1, andin a mono carboxylic anion to aluminum (trivalent cation) molar ratiobetween 0.1:1 to 1.2:1. The process involves reacting a mixturecomprising magnesium and aluminum cations and mono carboxylic anions inan aqueous slurry having a temperature of at least 40° C. and a pH of atleast 7. Generally speaking, a given synthesis of a HTL compound by anyof the methods taught in these patents was considered a success when theproduct of its chemical synthesis reaction (slurries typically wereheated and/or pressured to form a final dry product or precipitate)produces a given HTL compound having an x-ray diffraction pattern whichreasonably resembles that of a given card in the files of theInternational Center for Diffraction Data (“ICDD”)

[0037] In summarizing the prior art, it might be said that most methodsthat have been employed to produce anionic clay compounds, andespecially hydrotalcite-like, anionic clay compounds, usually involveprecipitation or slurry drying of a hydrotalcite-like product, washingand, optionally, heat treatment of the resulting dried slurry, orprecipitated, composition. Once made, these HTL compounds, or theirthermal decomposition products, have been employed as catalysts (e.g.,as vanadium passivators, SO_(x) additives, aldol condensation catalysts,water softening agents, and even medicines).

SUMMARY OF THE INVENTION

[0038] Applicant's contribution to this art has been to discover certainhereinafter described methods, whereby HTL compounds can be producedfrom compounds that do not exhibit HTL structures (e.g., as determinedby their XRD patterns), but which do exhibit HTL structures upon beingactivated by the processes of this patent disclosure. Applicant also hasdiscovered certain novel methods whereby anionic clays in general andhydrotalcite-like compounds in particular can be given certainattributes (increased hardness, density, etc.) that make such compoundsbetter suited for uses where these attributes are desirable, e.g., assorbents for various chemical species—but especially SO_(x) sorbents—andespecially those SO_(x) sorbents (and binder materials) used in FCCunits, as hydrocarbon catalysts, as water softening agents, etc.

[0039] Again, those compounds generally described as “anionic clays” inthe literature, and especially hydrotalcite, and HTL anionic claycompounds, will be collectively referred to as “HTL compounds” for thepurposes of this patent disclosure. More specifically this inventioninvolves formation of hydrotalcite-like compounds by certain novelproduction methods and the use of certain formed shapes (microspheroidalparticles, extrudates, pellets) containing those hydrotalcite-likecompounds produced by applicant's processing techniques. For example,these formed shapes (e.g., microspheroidal particles, pellets,extrudates, etc.) for certain specific catalytic uses (e.g., FCCoperations, SO_(x) sorption, water softener regeneration agents, etc.).Hence, the HTL compounds of this patent disclosure may constitute partof (or even all of) a given catalyst particle, pellet, extrudate, etc.By way of example the HTL compounds of this patent disclosure may beassociated with various binder or matrix forming materials known to thecatalyst making art. Indeed, the HTL compounds of this patent disclosuremay be used as catalysts per se (e.g., as hydrocarbon crackingcatalysts), as SO_(x) binding agents, or as catalyst binder materialsfor other catalyst materials. Hence, for the purposes of this patentdisclosure the term “catalyst” should be taken to mean not only thoseHTL compounds that have catalytic or SO_(x) binding activity in theirown right, but also those HTL compounds that are used as binders,matrices and/or carriers for other catalytically active compounds (e.g.,binders for metallic, SO_(x) oxidation catalysts such as compoundscontaining platinum, cerium and vanadium). These applications are allrelated to the fact that the HTL compounds produced by applicant'smethods can, among other ways, be characterized by their resistance tomechanical stresses and, hence, by their ability to function in thesevere environments associated with many chemical reactions.

[0040] Applicant's overall invention is primarily based upon a two step“activation” procedure that is generally comprised of heat treating andthen hydrating certain hereinafter described hydrotalcite-producing,precursor compounds. This two step process may, in some cases, beaugmented by an additional, but purely optional, heat treatment step(which may be referred to as Step 3 of applicant's process). These heattreated compounds may be thought of “collapsed” or “metastable,” HTLcompound-forming materials.

[0041] Applicant's invention has two general embodiments. The firstembodiment is a method for producing HTL compounds (e.g., anionic claycompounds, hydrotalcite per se, and various hydrotalcite-like compounds)from compounds that do not possess the structural characteristics of HTLcompounds. The manner by which this first embodiment of applicant'sinvention differs from prior art methods for making similar HTLcompounds is that applicant's initial HTL synthesis is carried out usingthose ingredients and those reaction conditions which are such that theydo not directly produce compounds having a HTL structure, but ratherproduce compounds that exhibit a HTL structure only after experiencingapplicant's hereinafter described activation process. Hence, in thefirst embodiment of this invention, an actual XRD determination that theproduct of applicant's initial slurry or precipitation-synthesisreaction does not produce a compound having an XRD pattern thatreasonably resembles that of a compound having the proper ingredientatoms (e.g., those of magnesium, aluminum, oxygen and hydrogen in thecase of HTL compounds) on file with the ICDD could be an optional stepin applicant's overall process.

[0042] It also should be specially noted, however, that applicant'ssynthesis products may well include “amorphous” (non-crystalline)materials as well as non-HTL, crystalline phases—and combinationsthereof. Indeed, the term “amorphous” as used herein could include (1)crystalline phases which have crystallite sizes below the detectionlimits of conventional x-ray diffraction techniques, (2) crystallinephases which have some significant degree of ordering, but which lack acrystalline diffraction pattern due to dehydration or dehydroxilization(such as in layered aluminosilicates), and (3) true amorphous materialswhich may exhibit short range order, but no long-range order, such as,for example, silica and borate glasses.

[0043] Whatever their physical form (crystalline or amorphous), theseprecursor, synthesis reaction products may be subjected to some form of“low temperature” (i.e., “low temperature” may be taken to mean lessthan about 250° C., for the purposes of this patent disclosure) dryingprocess before they undergo the heat treatment aspect of applicant'sactivation process. Such a low temperature drying process also mayinclude the physical formation of those powders, pellets, beads,extrudates, microspheroidal spheres or granule forms of these reactionproduct materials that may be required (or desired) for use of thesematerials as catalysts, sorbents, ion exchange agents, etc. This dryingstep should, however, be considered “optional” because the mostfundamental version of the first embodiment of applicant's inventioncould go directly to its heat treatment step.

[0044] This heat treatment step involves heating applicant's synthesisreaction products to a “medium temperature” (i.e., a temperature in therange of about 300° C. to about 850° C.). This heat treatment may becarried out for widely varying periods of time (e.g., from for about 0.1to about 24.0 hours. This 300° C.-850° C. heat treatment step maygenerally be referred to as Step 1 of applicant's overall “activation”process. It is more preferred, however, that Step 1 be conducted at atemperature on the low-end of this 300° C.-850° C. range. This treatmentmay be carried out at some preferred temperature (e.g., 450° C.) or atdifferent temperatures in this 300° C. to 850° C. range. Step 1, mediumtemperature, heat treatments in the range of about 400° C. to about 500°C. are, however, highly preferred. Temperatures at the upper end ofapplicant's 300°-850° C. range, such as temperatures ranging from about700°-850° C., are less preferred since various less desirable phases(hereinafter more fully described) may result from heating applicant'sprecursor, synthesis reaction products to such levels. The formation ofthese less desirable phases may diminish the precursor material'spotential to form maximum amounts of the HTL-containing phases that arethe object of applicant's processes.

[0045] These higher temperatures also are less preferred because theycome dangerously close to the 900° C. temperature at which aparticularly undesirable material—namely, spinel (MgAl₂O₄) begins toform. Again, applicant regards spinel formation as “anathema” to thisprocess because spinel can not be rehydrated. This is not to say howeverthat any other material, e.g., MgO, that be present in such a system attemperatures at or above 900° C., can not be employed for applicant'spurposes. For example, if applicant's hydrotalcite-like startingmaterial is converted into spinel (MgAl₂O₄) it becomes useless forapplicant's purposes; if, however, applicant's starting material isconverted into MgO, it still may be useful (e.g., as an SO_(x) sorbentagent).

[0046] In any event, temperatures of 900° C. or higher can be regardedas “high temperatures” for the purpose of this patent disclosure andthey are to be avoided as far as possible. This admonition also isconsistent with the teachings and spirit of the literature. That is tosay that nowhere does the literature even remotely suggests that spinelcan be reversibly hydrated into any other phase at ambient temperatures.By way of sharp contrast with this, the literature teaches that HTLcompounds such as applicant's, very decidedly possess the characteristicof rehydratability.

[0047] The literature also teaches that the basic structural buildingblock of HTL, the brucite structure, Mg(OH)₂, also possess this“rehydratability” characteristic. It is also known that, if the crystalsize of such materials grows significantly (as it does with increasinglyhigher thermal treatment temperatures)., then such “reversibility” iseventually lost. Consequently, the brucite layer no longer forms uponrehydration. This is the same situation applicant expected, and in factobserved, for various HTL compounds made by the teachings of this patentdisclosure. Indeed, applicant found that as temperature increases beyondcertain levels, an increase in a MgO-like material's crystallite size,as well as alumina and magnesium aluminate (spinel) formation,eventually do take place. Consequently, for maximum SO_(x) activity ofapplicant's HTL compounds, it is preferred that all the MgO in a givensystem remain with the HTL phase as opposed to reacting with otherphases and thereby rendering the MgO “inactive” e.g., inactive as aSO_(x) “pickup agent.” Again, this is best achieved by not usingtemperatures above about 850° C.

[0048] In any case, the heat treated product of Step 1 of applicant's“activation” process is then subjected to a hydration step. Thishydration step might be termed Step 2 of applicant's activationprocedure. It generally entails mixing the heat treated product of Step1 with a quantity of moisture which is such that heat is evolved fromthe heat treated precursor material/liquid (e.g., water), mixture. Themethod or manner of hydration to effect applicant's Step 2 will include,but not limited to such methods as spraying, impregnating and blunging.

[0049] In any case, the heat release produced by this hydration isindicative of the heat of formation of a HTL compound. Additionally,this heat release signifies the occurrence of the chemical reactionwhich is presumed to be the cause of the greatly improved physicalproperties of HTL compounds prepared by the methods of this patentdisclosure. It also should be noted here that in order to maximize theamount of HTL compound produced by this hydration step, the amount ofwater added should be substantial in quantity (on the order of 30-50weight percent of the dry, precursor material). Such amounts of waterare required in order to fully form HTL phases although less water willstill result in a material that exhibits a HTL phase; such a phase willnot, however, be “pure,” i.e., other collapsed HTL phases will bepresent (i.e., a MgO-like phase and/or a MgAl solid solution phase).

[0050] Again, depending on the hydration method to be employed, thepreviously noted “low temperature,” optional drying step also may beemployed in order to render a material having a desired amount ofphysical water. And, once again, this low temperature drying should notexceed about 250° C. because applicant has found that temperatures inexcess of this may result in a premature release of various interlayerions, water, crystalline water, or certain carbonates. In any case, theHTL compound product produced by applicant's hydration step will possessa crystalline structure which exhibits an x-ray diffraction pattern thatmay, and probably will, reasonably resemble a ICDD “card” for some HTLcompound that has a similar crystalline structure.

[0051] In some cases this hydrated product may again be “collapsed” by asecond heat treatment step which might be called step 3 of applicant'sprocess (e.g., Step 3 heat treatments at temperatures ranging from about300° C. to 850° C. and preferably at 400° C. to 500° C.) in order toremove its interstitial water so that the resulting material is bettersuited to certain uses such as a SO_(x) sorbent in a FCC unit. Compoundscreated by this third step may be used for any of the purposes for whichthe HTL compounds created by applicant's Step 1 and Step 2 materials maybe used.

[0052] From a broad conceptual point of view, the most fundamentalversion of the first embodiment of applicant's invention might bethought of as being based upon: (1) a “delay” in the production of ahydrotalcite-like compound end product relative to the point at whichanalogous hydrotalcite-like compounds have been made by prior artproduction methods, (2) heat treatment (single stage or multiple stage)of these “not yet” (e.g., with this “not yet” quality or state beingdetermined by XRD methods) hydrotalcite-like materials and (3) hydrationof the these heat treated materials to form hydrotalcite-like compounds.Stated another way, it might be said that the goal of applicant'sinitial synthesis or chemical reaction step is to not make as much of asubject, end product, HTL compound as possible (e.g., not to make asmuch hydrotalcite as possible), but rather to make as little of thedesired end product compound, (e.g., to make as little hydrotalcite) aspossible.

[0053] In any event, applicant's first general process may generallyemploy any combination of those HTL compound creating startingingredients (e.g., magnesium-containing compounds having less reactiveanions and aluminum-containing compounds having less reactive anions)and any of those reaction conditions (e.g., short reaction aging times,neutral pH levels, and ambient temperatures reaction conditions) thatmay serve to—and, indeed, strive to—produce a resulting slurry orprecipitate material that does not exhibit the crystalline structure ofthe HTL compound that ultimately will be exhibited by applicant's endproduct hydrotalcite-like compound. In fact, the precursor compoundsobtained by the initial chemical reaction step of applicant's firstprocess may well be entirely amorphous materials having no HTL structurewhatsoever.

[0054] In the second embodiment of applicant's invention, however, ahydrotalcite-like compound is purposely used as the starting material,or as a precursor compound. That is to say, that a hydrotalcite-likestarting material can be purchased commercially—or it can be synthesizedby use of any of the many methods known to this art and then be employedaccording to the teachings of this patent disclosure. In either case,however, applicant's process calls for heat treatment of thehydrotalcite-like compound (however obtained) to form a “collapsed” or“metastable” material. This heat treatment also may be thought of asStep 1 of this second embodiment of applicant's invention. The collapsedor metastable material of this second embodiment is then hydrated toagain form a hydrotalcite-like compound. This hydration may be thoughtof as Step 2 of this second embodiment of applicant's invention.Applicant has found that this “roundabout” method of producing ahydrotalcite-like compound (from a hydrotalcite-like compound) is wellworth the extra effort because the resulting hydrotalcite-like compoundwill be harder and/or more dense than the original hydrotalcite-likecompound from which the resulting HTL compound was made.

[0055] Stated another way, the starting ingredient in the secondembodiment of applicant's invention already will be a rehydratablehydrotalcite-like compound. This may be evidenced, for example, by thefact that it already generally displays XRD peaks that resemble those ofa known HTL compound having the same ingredients (e g., Mg and Al). Inany case, this hydrotalcite-like compound starting material is then heattreated to convert it into a “collapsed” or “metastable” compound suchas those described in the Miyata reference, or in the '118 patent. TheStep 2, heat treatment of the second embodiment of this invention can beconducted at a single preferred temperature (e.g., 450° C.) or at two ormore distinct temperatures in the general temperature range of 300° C.to 850° C., e.g., at a first, lower temperature, (e.g., at 300° C.)followed by a second temperature heat treatment (e.g., at 400° C. to500° C.). Here again, however, temperatures greater than about 850° C.are to be avoided in this second embodiment of applicant's process forthe same reasons they were to be avoided in the first embodiment. Forexample, if the original synthesis compound were hydrotalcite, and itexperienced a 900° C. heat treatment temperature for any significantperiod of time in the second embodiment of applicant's invention, it toowould in fact be converted it into spinel (MgAl₂O₄) and, thus, would berendered useless for the purposes of practicing this invention. Hereagain, any hydrotalcite converted to MgO by such high temperatureswould, however, still be potentially useful in carrying out functionsfor applicant's end product materials.

[0056] In any case, after the hydrotalcite-like compound of this secondembodiment is heat treated to an extent that it takes on a “collapsed”or “metastable” form, it can then hydrated (e.g., in a water system at20-100° C. for at least 0.1 hours) in the same manner employed in thefirst embodiment of this invention to again form a similarhydrotalcite-like compound. Again, this “hydrotalcite-like compound—tohydrotalcite-like compound” production process is not a useless,redundant or roundabout journey because the hydrotalcite-like compoundsresulting from this second embodiment of applicant's invention will, infact, have certain improved physical and/or chemical properties (e.g.,greater density, attrition resistance, catalytic activity, etc.)relative to those comparable properties possessed by the originalhydrotalcite-like compound from which the resulting or end producthydrotalcite-like compound was derived. And as in the case of the firstembodiment of this invention, the resulting HTL compound of this secondembodiment can be once again heat treated (this may be thought of asStep 3 of this second embodiment) at temperatures ranging from about300° C. to 850° C. in order to obtain a yet harder material whose lossof water due to this second heat treatment may render the resultingmaterial better suited to certain uses (e.g., as a SO_(x) absorbent in aFCC unit). That is to say that Step 3 can be employed to give theresulting material (here again, a “collapsed” or “metastable” HTLcompound-forming material) improved physical properties relative tothose HTL compounds that are not subjected to this additional heattreatment process.

[0057] The anionic compounds that can be produced by the hereindescribed processes will most preferably have a chemical structure:

[M_(m) ²⁺(OH)_(2m+2n)]A_(n/a) ^(a−).bH₂O

[0058] wherein M²⁺ and N³⁺ are cations, m and n are selected such thatthe ratio of m/n is about 1 to about 10, a will have a value of 1, 2 or3, A is an anion with charge of −1, −2 or −3, and b will range between 0and 10, are highly preferred. The most preferred elements for “M” in theabove structure will be Mg, Ca, Zn, Mn, Co, Ni, Sr. Ba, Fe and Cu Themost preferred element for “N” will be Al, Mn, Fe, Co, Ni, Cr, Ga, B, Laand Ce. The most preferred elements for “A” with charge a—will be CO₃²⁻, NO₃ ⁻, SO₄ ²⁻, Cl⁻ and OH⁻, Cr⁻, I⁻, SO₄ ²⁻, SiO₃ ²⁻, HPO₃ ²⁻, MnO₄²⁻, HGaO₃ ²⁻, HVO₄ ²⁻.ClO₄ ⁻ and BO₃ ²⁻ and mixtures thereof.

[0059] Applicant generally has found that HTL compounds made by eitherof the two general embodiments of this invention are usually at leastabout 10% harder and/or 10% more dense than comparable HTL compoundsmade from the same ingredients by prior art production methods. Thesephysical attribute(s), e.g., of hardness and/or greater density, makesthose catalysts, sorbents, catalyst binders and ion exchange agents(e.g., water softener agents) made from applicant's hydrotalcite-likecompounds more attrition resistant—and hence longer lasting—especiallyin a fluid catalytic converter (“FCC”) environment. Applicant'sresulting compounds also have an improved ability to be regenerated(e.g., with respect to their ability to continue to serve as SO_(x)sorbents, hydrocarbon cracking (or hydrocarbon forming) catalysts, ionexchange agents, etc.) after having experienced temperatures which wouldpermanently deactivate analogous anionic clays (such as analogoushydrotalcite-like compounds) made by prior art manufacturing methods.Indeed, these improved physical attributes can be thought of as evenfurther helping to define applicant's materials and distinguish themfrom analogus HTL compounds made by prior art methods. That is to saythat, if applicant's “activation” procedures (using Steps 1 and 2 orusing Steps 1, 2 and 3) produce, say, a hydrotalcite-like compoundexhibiting greater hardness and/or greater density than a comparablehydrotalcite-like compound made by other methods, then these qualitiesmay help to distinguish applicant's “hydrotalcite-like compounds” fromthose made by prior art methods.

[0060] Expressed in patent claim language, there are several generalembodiments of applicant's processes for making and using the HTLcompounds of this patent disclosure. The differences between themgenerally revolve around: (1) whether or not the material produced bythe original synthesis reaction is a non-anionic clay compound (e.g., anon-hydrotalcite-like compound) or an anionic clay compound (e.g., ahydrotalcite-like compound), (2) whether or not the non-anionic claycompound or the anionic clay compound is dried and heat treated in oneor more stages before it is eventually hydrated and (3) whether or notthe resulting HTL compound is used as a catalyst (or catalyst binder), aSO_(x) sorbent, an ion exchange agent, etc. Some of these embodimentsmay be expressed in patent claim language as follows:

[0061] 1. A process for making an anionic clay compound, said processcomprising:

[0062] (1) preparing a reaction mixture comprising a divalentmetal-containing compound and a trivalent metal-containing compoundunder conditions such that a product obtained from the reaction mixtureis a non-anionic clay compound;

[0063] (2) heat treating the non-anionic clay compound to create a heattreated, non-anionic clay compound;

[0064] (3) hydrating the heat treated, non-anionic clay compound toobtain an anionic clay compound.

[0065] 2. A process for making an anionic clay compound, said processcomprising:

[0066] (1) preparing a reaction mixture comprising a divalentmetal-containing compound and a trivalent metal-containing compoundunder conditions such that a product obtained from the reaction mixtureis a non-anionic clay compound;

[0067] (2) low temperature treating the non-anionic clay compound toobtain a low temperature treated, non-anionic clay compound;

[0068] (3) medium temperature treating the non-anionic clay compound tocreate a precursor for an anionic clay compound;

[0069] (4) hydrating the precursor for an anionic clay compound toobtain an anionic clay compound.

[0070] 3. A process for making an anionic clay compound, said processcomprising:

[0071] (1) preparing a reaction mixture comprising a divalentmetal-containing compound and a trivalent metal-containing compoundunder conditions such that a product obtained from the reaction mixtureis a non-anionic clay compound;

[0072] (2) converting the non-anionic clay compound into a desiredphysical form;

[0073] (3) heat treating the non-anionic clay compound to obtain acollapsed, heat treated, non-anionic clay compound;

[0074] (4) hydrating the collapsed, heat treated, non-anionic claycompound to obtain an anionic clay compound.

[0075] 4. A process for making a hydrotalcite-like compound, saidprocess comprising:

[0076] (1) preparing a reaction mixture comprising analuminum-containing compound and a magnesium-containing compound underconditions such that a product obtained from the reaction mixture is anon-hydrotalcite-like compound;

[0077] (2) heat treating the non-hydrotalcite-like compound to create aheat treated, non-hydrotalcite-like compound;

[0078] (3) hydrating the heat treated, non-hydrotalcite-like compound toobtain a hydrotalcite-like compound.

[0079] 5. A process for making a hydrotalcite-like compound, saidprocess comprising:

[0080] (1) preparing a reaction mixture comprising analuminum-containing compound and a magnesium-containing compound underconditions such that a product obtained from the reaction mixture is anon-hydrotalcite-like compound;

[0081] (2) low temperature treating the non-hydrotalcite-like compoundto obtain a low temperature treated, non-hydrotalcite-like compound;

[0082] (3) medium temperature treating the non-hydrotalcite-likecompound to create a precursor for a hydrotalcite-like compound;

[0083] (4) hydrating the precursor for a hydrotalcite-like compound toobtain a hydrotalcite-like compound.

[0084] 6. A process for making a hydrotalcite-like compound, saidprocess comprising:

[0085] (1) preparing a reaction mixture comprising analuminum-containing compound and a magnesium-containing compound underconditions such that a product obtained from the reaction mixture is anon-hydrotalcite-like compound;

[0086] (2) converting the non-hydrotalcite-like compound into a desiredphysical form;

[0087] (3) heat treating the non-hydrotalcite-like compound to obtain acollapsed, heat treated, non-hydrotalcite-like compound;

[0088] (4) hydrating the collapsed, heat treated, non-hydrotalcite-likecompound to obtain a hydrotalcite-like compound.

[0089] 7. A process for making a relatively hard, hydrotalcite-likecatalyst, said process comprising:

[0090] (1) preparing a reaction mixture comprising analuminum-containing material and a magnesium-containing compound underconditions such that a product obtained from the reaction mixture is arelatively soft, hydrotalcite-like compound;

[0091] (2) converting the relatively soft, hydrotalcite-like compoundinto a form suitable for use as a catalyst;

[0092] (3) heat treating the relatively soft, hydrotalcite-like compoundto obtain a heat treated, precursor for a relatively hard,hydrotalcite-like catalyst; and

[0093] (4) hydrating the heat treated, precursor for a relatively hard,hydrotalcite-like catalyst to obtain a relatively hard,hydrotalcite-like catalyst.

[0094] 8. A process for making a relatively hard, hydrotalcite-likecatalyst, said process comprising:

[0095] (1) preparing a reaction mixture comprising analuminum-containing compound and a magnesium-containing compound underconditions such that a product obtained from the reaction mixture is arelatively soft, hydrotalcite-like compound;

[0096] (2) converting the relatively soft, hydrotalcite-like compoundinto a form suitable for use as a catalyst;

[0097] (3) low temperature treating the relatively soft,hydrotalcite-like compound to obtain a low temperature treated,relatively soft, hydrotalcite-like compound;

[0098] (4) medium temperature treating the relatively soft,hydrotalcite-like compound to create a precursor for a relatively hard,hydrotalcite-like catalyst; and

[0099] (5) hydrating the precursor for a relatively hard,hydrotalcite-like catalyst to obtain a relatively hard,hydrotalcite-like catalyst.

[0100] 9. A process for making a relatively hard, hydrotalcite-likeSO_(x) sorbent, said process comprising:

[0101] (1) preparing a reaction mixture comprising analuminum-containing compound and a magnesium-containing compound underconditions such that a product obtained from the reaction mixture is arelatively soft, hydrotalcite-like compound;

[0102] (2) converting the relatively soft, hydrotalcite-like compoundinto a physical form suitable for use as a SO_(x) sorbent;

[0103] (3) heat treating the relatively soft, hydrotalcite-like compoundto obtain a precursor for a relatively hard, hydrotalcite-like SO_(x)sorbent; and

[0104] (4) hydrating the precursor for a relatively hard,hydrotalcite-like SO_(x) sorbent to obtain a relatively hard,hydrotalcite-like SO_(x) sorbent.

[0105] Because the HTL compounds of this patent disclosure are harderthan HTL compounds made by prior art processes, they present a methodwhereby the useful life of a catalyst or sorbent system (such as thoseemployed in FCC units or fixed bed units) can be extended. Thisextension of a catalyst's (or sorbent's) useful life will take placewhen the HTL compounds of this patent disclosure are used in their ownright, e.g., as hydrocarbon cracking or forming catalysts, SO_(x)sorbents, etc., or when these HTL compounds are used as binders,matrices, supports, or carriers for other catalytically active materials(e.g., when they are used as binders for SO_(x) oxidant metals).

[0106] Thus, using SO_(x) sorption in a FCC unit used to refinepetroleum as an example, the method of extending the useful life of anSO_(x) , sorbent (or catalyst) may be expressed in patent claim languagein the following manner:

[0107] A method for extending the useful life of a SO_(x) sorbent systemused in a FCC unit being employed to refine a petroleum feedstock, saidmethod comprising: employing a HTL compound made by use of a process ofthis patent disclosure as a SO_(x) sorbent system in the FCC unit andwherein the HTL compound is in the form of a microspheroidal particlespecies whose primary function is sorbing SO_(x) produced by refining asulfur-containing petroleum.

[0108] Such a HTL compound-containing particle species may furthercomprise a binder agent selected group consisting of magnesiumaluminate, hydrous magnesium silicate, magnesium calcium silicate,calcium silicate, alumina, calcium oxide and calcium aluminate.

[0109] Expressed in patent claim language, such a method for extendingthe useful life of a SO_(x) additive system comprised of a SO₂→SO₃oxidation catalyst and a SO₃ sorbent may comprise:

[0110] (1) employing the SO_(x) additive system in the form of at leasttwo physically distinct particle species wherein a first particlespecies contains the SO₂→SO₃ oxidation catalyst component and carriesout a primary function of oxidizing sulfur dioxide to sulfur trioxideand the second particle species is physically separate and distinct fromthe first particle species and carries out a primary function of sorbingthe SO₃ produced by the SO₂→SO₃ oxidation catalyst;

[0111] (2) employing the SO₂→SO₃ oxidation catalyst in the form of aparticle species that comprises: (a) a sulfur SO₂→SO₃ oxidation catalystcomprised of a metal selected from the group consisting of cerium,vanadium, platinum, palladium, rhodium, molybdenum, tungsten, copper,chromium, nickel, iridium, manganese, cobalt, iron, ytterbium, anduranium; and (b) a binder made from a material selected from the groupof metal-containing compounds consisting of hydrotalcite-like compounds,calcium aluminate, aluminum silicate, aluminum titanate, zinc titanate,aluminum zirconate, magnesium aluminate, alumina (Al₂O₃), aluminumhydroxide, an aluminum-containing metal oxide compound (other thanalumina (Al₂O₃)), clay, zirconia, titania, silica, clay andclay/phosphate material; and

[0112] (3) using the SO₃ absorbent component in the form of a secondparticle that comprises a hydrotalcite-like compound made by use of an“activation process” of this patent disclosure.

[0113] This activation process may involve use of Step 1 and Step 2 (orSteps 1, 2 and 3) upon a non-hydrotalcite-like starting material or ahydrotalcite-like starting material. Any of the HTL compounds may beused in FCC systems wherein the SO_(x) sorbent particle speciescomprises from about 10 to about 90 weight percent of the overall SO_(x)additive system (i.e., the SO_(x) sorbent particle species and theSO₂→SO₃ oxidant particle species). Such an overall, SO_(x) additivesystem will, in turn, normally comprise from about 0.5 to about 10.0weight percent of a bulk hydrocarbon cracking catalyst (e.g., zeolite)SO_(x) additive system.

[0114] Next, it should be understood that the HTL compounds made by anyof these methods may be used in any way that the prior art has usedhydrotalcite-like compounds made by any prior art method (e.g., they maybe used as sorbents and especially SO_(x) sorbents, hydrocarbon crackingcatalysts, e.g., for use in fixed bed or fluid bed systems, catalystcarrier or binder-materials, anion exchangers (e.g., water softeneragents, etc.) acid residue scavengers, stabilizers for polymers,medicines, etc.). Applicant's HTL compounds are, however, particularlyuseful where the attributes of physical hardness, toughness, or greaterdensity are especially desired (e.g., when they are used in FCC units asSO_(x) sorbents, catalysts and catalyst binders or carriers).

BRIEF DESCRIPTION OF THE DRAWINGS

[0115]FIG. 1 is a XRD pattern for a 2Mg/1Al ratio HTL precursor slurry.

[0116]FIG. 2 is a XRD pattern for a 2Mg/1Al ratio HTL precursor slurryin which the slurry has been heat aged at about 80-85° C.

[0117]FIG. 3 is a XRD pattern for a 2Mg/1Al ratio HTL precursor slurryin which the slurry has been heat aged at about 80-85° C. for a longerduration than the material whose XRD is depicted in FIG. 2.

[0118]FIG. 4 is the XRD for a 2Mg/1Al ratio precursor material that hasbeen heat age treated; and wherein the effects of an amorphous phaseassociated with that crystalline phase 2Mg/1Al ratio HTL precursor havebeen subtracted from the XRD pattern.

[0119]FIG. 5 depicts (via XRD pattern changes) the various phase changesthat take place as a result of the activation process of this patentdisclosure.

[0120]FIG. 6 gives the XRD pattern for a 2Mg/1Al ratio HTL phaseproduced using applicant's activation process in a case where thestarting 2Mg/1Al ratio HTL precursor slurry was not heated.

[0121]FIG. 7 depicts the XRD for a 2Mg/1Al ratio HTL phase produced byapplicant's activation process using a heated 2Mg/1Al HTL precursorslurry.

[0122]FIG. 8 shows the XRD pattern for a 2Mg/1Al ratio phase materialplus oxidants made by applicant's process.

[0123]FIG. 9 shows the XRD for a Mg/Al system activated by applicant'sprocess and wherein the system has a 5Mg/1Al molar ratio.

[0124]FIG. 10 depicts the effects of a one hour, 500° C. heat treatmenton precursor phase with oxidants.

[0125]FIG. 11 shows XRD for a 3Mg/1Al/oxidant (Ce, V) system where theoxidants were added to the precursor slurry after a one hour, 732° C.calcination and wherein the oxidants were added to a precursor slurry.

[0126]FIG. 12 shows XRD for a 3Mg/1Al oxidant (Ce, V) system wherein theoxidants were added to a precursor slurry and wherein the system wasactivated through use of applicant's methods at 732° C.

[0127]FIG. 13. is a TGA/SO_(x) Sorption and Release trace for a 3Mg/1AlHTL system prepared by applicant's process.

DETAILED DESCRIPTION OF THE INVENTION

[0128] Even though this invention is broadly concerned with anionicclays in general, it is mostly illustrated through discussions, data andworking examples that focus on those anionic clays known ashydrotalcite-like (“HTL”) compounds. Applicant does this because (1) HTLcompounds are perhaps the most readily formulated anionic claycompounds, (2) they are the most well studied and reported anionic claycompounds in the literature and because (3) they are, in fact, the mostpreferred compounds for actual practice of applicant's invention. Thecrystalline structures of some of the more preferred forms of HTLcompounds for the practice of this invention reasonably resemble thoseof: (1) magnesium aluminum hydroxides, (2) magnesium aluminum hydroxidehydrates and (3) magnesium aluminum hydroxide carbonate hydrates. Theyare preferably made from compositions primarily comprised of (1) amagnesium-containing compound and (2) an aluminum-containing compound(e.g., an alumina sol, alumina gels or crystalline alumina) and,optionally, (3) other ingredients such as metal oxidants and bindermaterials commonly used to make certain end product forms of such HTLcompounds (FCC catalysts, SO_(x) sorbents, anion exchange pellets,etc.).

[0129] Some particularly useful magnesium-based compounds for creatingapplicant's HTL compounds will include magnesium hydroxy acetate,magnesium acetate, magnesium hydroxide, magnesium nitrate, magnesiumhydroxide, magnesium carbonate, magnesium formate, magnesium chloride,magnesium aluminate, hydrous magnesium silicate and magnesium calciumsilicate.

[0130] Some particularly useful aluminum-based compounds for creatingapplicant's HTL compounds will include aluminum acetate, aluminumnitrate, aluminum hydroxide, aluminum carbonate, aluminum formate,aluminum chloride, hydrous aluminum silicate and aluminum calciumsilicate. In the case of the first embodiment of this invention, thesemagnesium-containing compounds and aluminum-containing compounds shouldbe employed such that the product of their initial reaction does notproduce the HTL compound that will ultimately be produced by applicant'sinvention. By way of example only, HTL compound formation by thisinitial reaction can be thwarted at this point in the production processby employing any synthesis-influencing factor selected from the groupconsisting of (1) use of less reactive magnesium-containing and/or lessreactive aluminum-containing compounds (e.g., use of hydroxides insteadof acetate forms of magnesium), (2) use of particulate ingredientsrather than those in true solution, (3) use of relatively short reactionperiods (e.g., less than 0.1 hours), (4) use of “neutral” pH levels(e.g., 6-8 pH levels) and (5) use of relatively low temperature reactionconditions (e.g., less than 30° C.).

[0131] Additionally, for use in those applications where other functions(e.g., oxidation of SO₂→SO₃) is a part of the proposed end usage ofapplicant's HTL compounds (e.g., when they are to be used as FCCcatalyst, or SO_(x) sorbent particles), any number of well knownoxidants may be employed in conjunction with applicant's HTL compounds.Such oxidants would include, for example, platinum, those compoundswhich form oxides of the rare earth metals, oxides of transition metals,etc. Such oxidants can also be associated with the HTL compounds of thispatent disclosure by impregnating dried forms of these HTL compoundswith solutions containing ions of such oxidant metals.

Ingredient Proportions

[0132] TABLE I illustrates some representative relative concentrationsof several HTL compositions that can be made by the teachings of thispatent disclosure that are especially useful as SO_(x) sorbentformulations. They are given in Table I, on a dry oxide basis, both withand without oxidants. TABLE I Mg/Al (molar) (ratio) 2/1 3/1 5/1 MgO, w %61.3 70.4 79.8 Al₂O₃, w % 38.7 29.6 20.2 MgO, w % 52.1 59.8 67.8 Al₂O₃,w % 32.9 25.2 17.2 CeO₂, w % 12.0 12.0 12.0 V₂O₅, w % 3.0 3.0 3.0

[0133] It also should be appreciated that the HTL compounds of thispatent disclosure can be used alone (that is to say that they can actcatalytically, as sorbents, etc. and serve as their own binder or matrixmaterial) or they can be associated with various catalyst binder ormatrix-forming materials that are well known to those skilled in thecatalyst and/or sorbent making arts. Indeed, such binder ormatrix-forming materials may constitute up to about 99 weight percent ofan overall catalyst or sorbent material (be it a microspheroidalparticle, pellet, extrudate, etc.) in which the HTL compounds of thispatent disclosure are employed. By way of example only, such catalyst,SO_(x) binder or matrix-forming materials may be magnesia, alumina,aluminum-containing metal oxide compounds, aluminum hydroxide, clay,zirconia, titania, silica, clay and/or clay/phosphate materials.

[0134] This all goes to say that, even thought the HTL compounds of thispatent disclosure may serve as both an SO sorbent and as its own bindermaterial in the practice of this invention, applicant's SO sorbentcatalysts (as well as any other solid forms of these HTL compounds) may,more preferably, comprise at least one HTL compound made by theprocesses of this invention and at least one, chemically different,binder, matrix, support, etc. material for that HTL compound. Forexample, a SO_(x) additive catalyst intended for use in a FCC unit maybe comprised of a hydrotalcite-like compound supported by, say, acalcium aluminate binder.

[0135] Next it should be again noted that when applicant's HTL compoundsare used as SO sorbent components, or catalysts or anion exchangeagents, etc., they may be so used alone—e.g., as separate and distinctSO sorbent particles or they may be used with other active materialswhich may be present as different particle species or as components ofthe particle species that employ the HTL compounds of this patentdisclosure. By way of example only, such particles may be provided withtheir own SO₂→SO₃ oxidation catalyst ingredients. Moreover, one or moreparticle species that make up applicant's SO sorbent component (s) maybe—as an option, and not a requirement —provided with SO₂→SO₃ oxidationcatalysts selected from the group consisting of cerium, vanadium,platinum, palladium, rhodium, iridium, molybdenum, tungsten, copper,chromium, nickel, manganese, cobalt, iron, ytterbium, and uranium. Ofthese possible SO₂→SO₃ oxidation catalysts, ceria and vanadia haveproven to be a particularly effective SO₂ oxidation catalyst when an SO₂oxidant is used in conjunction with applicant's HTL compound based, SO₃absorbents. It also should be understood, however, that SO₂→SO₃oxidation catalysts of this kind also could be placed upon an entirelyseparate and distinct particle species that is admixed with thoseparticles that are made with applicant's HTL compounds.

[0136] Preparation and Processing

[0137] As previously discussed, the first embodiment of this invention,among other things, requires that an amorphous and/or non-crystallineHTL phase be present at the end of the slurry or precipitate preparationstep. A diffraction pattern for a representative material of this kindis shown in FIG. 1. FIGS. 2-3 show the effects of “low temperature”(i.e., less than about 100° C.) heat aging the material whose XRDpattern is shown in FIG. 1. These figures show the presence ofsignificant amorphous phases, as well as non-HTL crystalline phases. Theparticular materials associated with these figures were prepared using a2Mg/1Al molar ratio. In one case, illustrated in FIG. 1, the slurry wasnot heat aged, while the material whose XRD pattern is shown in FIGS. 2and 3 was heat aged at about 80-85° C. FIGS. 2 and 3 show that uponbeing subjected to such low temperature heating, a new crystalline phasenucleates and grows with increasing aging time. FIG. 4 shows thecrystalline portion of the phase that was shown in FIG. 2. That is tosay that the effects of the presence of the amorphous material that arepresent in FIG. 2 are “subtracted out” of the XRD pattern shown in FIG.4.

[0138]FIG. 5 shows the changes in crystal structure at various steps inapplicant's “activation” process. The top two curves in this plot(respectively labeled “2Mg/1Al Precursor before heat aging” and “2Mg/1AlPrecursor after heat aging”) already have been discussed as part of theprevious discussion of FIGS. 1 to 4. The trace in FIG. 5 labeled “heattreated” is representative of the observed phases of HTL structuresfollowing Step 1 of applicant's activation process. The trace labeled“heat treat+hydrate (activated HTL)” depicts the results of Step 2 ofapplicant's activation process. Clearly, an HTL structure has beencreated. This is evidenced by the presence of all major peaks of an HTLcompound, including peaks at about 11.271 degrees, 22.700 degrees and34.358 degrees manifesting their presence. It also should be noted thatFIG. 5 includes the effects of the CeO₂ component that was added duringthe synthesis reaction and whose most prominent peaks manifestthemselves at 28.555 degrees, 47.479 degrees and 56.335 degrees.

[0139]FIGS. 6 and 7 plot the XRD pattern for a 2Mg/1Al HTL compound thatis produced using applicant's activation process. The compound thatgenerated FIG. 6 was derived from an un-heated slurry, while that forFIG. 7 was heat aged. The “stick diagram” (vertical lines of differentheights at the appropriate 2θ positions) for the “best matching” ICDDcard is superimposed on each of these two plots. In this case the “bestmatch” was with ICDD “card” 35-965 for Mg₆Al₂(OH)₁₈—4.5H₂O. It alsoshould be emphasized here that certain other ICDD cards (e.g., ICDD card22-700 for hydrotalcite) reasonably “matched” the peak positions andintensities to give reasonably close correlations, but this particularHTL compound has 2θ peak positions that are nearly identical to those ofthe 35-965 card. This HTL compound also displayed XRD intensities whichhad the fewest inconsistencies relative to those of the severalcandidate cards that were considered. The lattice parameters of both theaged and non-aged slurry example are compared in TABLE II with the “bestmatching” card, namely, ICDD card 35-965. TABLE II ICDD Card h2 Mg/1AlHTL 2 Mg/1Al HTL 35-965 (not aged) (aged slurry) a, Angstrom 3.054 3.0573.060 c, Angstrom 23.40 23.05 23.08 alpha, degrees 90 90 90 beta,degrees 90 90 90 gamma, degrees 120 120 120

[0140] It can be seen that the lattice parameter, “a,” of applicant's2Mg/1Al HTL compound is nearly identical to that of the card, whilelattice parameter “c” is substantially lower. Applicant believes thatthis signifies that the amount of Al³⁺ substituted into the brucite-likestructure is nearly identical to that of the 35-965 card material, whilethe variation in lattice parameter c is due to the nature and amount ofinterlayer water and charge-balancing anions located in the interlayer.

[0141]FIG. 8 shows the XRD patterns for the same 2Mg/1Al HTL compoundused to generate FIGS. 6 and 7 except that 12 weight percent CeO₂ and 3weight percent V₂O₅ components are present by virtue ofcerium-containing compound (e.g., cerium nitrate) being added to theslurry formulation after reacting the magnesium and aluminum containingcomponents together. It also should be noted that, with the exception ofthe effects of the CeO₂ present (ICDD Card 34-394) in this system, thepattern is very similar to those samples containing no oxidants (again,see FIGS. 6 and 7).

[0142] The following TABLE III compares XRD patterns for HTL compoundswith, and without, oxidants as compared to the patterns of the “mostclosely matching” ICDD card. This comparison shows that the presence ofthe oxidants in no way affects the structure of the HTL compound. TABLEIII ICDD Card no with oxidants 35-965 oxidants CeO₂ and V₂O₅ a, Angstrom3.054 3.057 3.046 c, Angstrom 23.40 23.05 23.07 alpha, degrees 90 90 90beta, degrees 90 90 90 gamma, degrees 120 120 120

[0143] Thus, based upon these and other findings, applicant hasconcluded that, within a reasonable experimental error allowance forthis kind of analysis, no appreciable difference in crystal structurecan be observed between HTL compounds associated with CeO₂ and V₂O₅oxidants and those without such oxidants.

[0144] Diffraction patterns showing the effect of a higher Mg/Al ratio(i.e., 5:1) in the HTL structural formation are shown in FIGS. 9. Inaddition to the HTL compound and oxidant CeO₂, a small amount ofmagnesium hydroxide (ICDD Card 7-239) was observed in the pattern shownin FIG. 10. This result is consistent with results published in theliterature in that the maximum HTL formation has been determined byother workers in this art (e.g., Miyata) to be in the Mg/Al ratio rangeof 2-4. Since the sample that generated FIG. 10 was prepared at a5Mg/1Al ratio, the amount of magnesium ions present in such a systemexceeded the limit of their solubility in the brucite layer—hence amagnesium hydroxide phase was formed and manifested itself in this way.

[0145]FIG. 10 shows the crystal structure present for HTL precursorsmaterials having differing Mg/Al ratios just prior to Step 2 ofapplicant's activation process. Of particular interest here are the“shoulders” on the 43 degree and 62 degree “MgO-like” peaks of thesediffractograms. It can be seen that, as the Mg/Al ratio increases from2:1 to 5:1, the magnitude of these peaks diminishes to a level wherethey become undetectable. This is indicative of a metastable aluminaphase, with or without a small amount of magnesium oxide dissolved inthe lattice. Additionally, this result shows that alumina is present,primarily within the lattice of the MgO, and hence the term “MgO-like”,compounds also might be applied to those HTL compounds that haveundergone applicant's Step 2 heat treatment—but no hydration. Themetastable alumina phase is a direct corollary to the 5Mg/1Al materialpreviously discussed wherein the presence of “too many” Mg ions resultedin an excess that manifested itself as a magnesium hydroxide phase. Inthis case, “too low” a Mg/Al ratio results in an excess of alumina whichcan be regarded as a slightly magnesia-rich alumina phase. Thisobservation has been made in the literature as well; see, for example,Gastuche et al, Mixed Magnesium-Aluminum Hydroxides, Clay Minerals 7, 7(1967), particularly noting FIG. 1 therein. See also the previouslynoted Miyata reference, (and especially page 52 thereof).

[0146] Thus, for maximum HTL formation by applicant's processes,hydrotalcite-like compounds having a Mg/Al ratio in the 2-4 range arehighly preferred. When the Mg/Al ratio drops below 2, a HTL structurecan result, but it will be mixed with alumina and or amagnesium-aluminum solid solution phase. The lattice parameter, a, ofsuch a system, however, generally, will remain unchanged at about 3.04Angstroms. In a system having a Mg/Al ratio in the range of 2-4, thelattice parameter, a, will increases with a linear relationship towardan end-point associated with magnesium hydroxide of 3.14-3.15 Angstroms.Above a Mg/Al ratio of 4, the lattice parameter continues to increasefurther, but magnesium hydroxide will accompany the HTL phase formation.See again, for example, the previously cited Miyata reference and theGastuche et al. reference (and especially FIG. 1, on pg 182 thereof).

[0147] The effects of increased temperature of applicant's activationprocess with respect to crystal structure was also studied. This studyverified the literature's pronouncements with respect to the temperatureat which spinel is formed from hydrotalcite. For example, applicantsubjected a commercially available hydrotalcite compound to such arising temperature regime in order to verify the temperature at whichspinel is formed from hydrotalcite. The commercially availablehydrotalcite was Alcoa's HTC-30® product (which has a 3:1 Mg/Al molarratio and is therefore well suited to use in the second embodiment ofapplicant's invention), and it was subjected to temperatures that rangedfrom 250° C. to 1200° C. This test showed MgO-like phase formationcommencing at 400° C. and spinel formation commencing at 900° C.

[0148] The results of some other analogous heat treatments, carried outat higher heat treatment temperatures, is presented in FIGS. 11 and 12.In these increased temperature studies, a 732° C. temperature was usedfor one hour as the heat treatment aspect of applicant's overall“activation” step since the literature states that this is near theupper-end of preferred temperature for maximum HTL phase formation. Inany case, no appreciable differences in structure are noted beyond thosealready noted for lower temperature activations (e.g., at 450-500° C.).

[0149] TGA-SO_(x) Testing of Sorbents

[0150] A modified Thermal Gravimetric Analysis (TGA) technique is usedby many laboratories worldwide to evaluate the relative SO_(x) sorbentperformance of different compositions. This modified technique employstwo tests, which are carried out at different temperatures. The firsttest is a SO_(x) “pickup” In this aspect of the TGA test, a furnace isramped up to about 700° C. in an inert gas and allowed to equilibrate. Agas mixture containing SO₂ and O₂ is then introduced into the reactorfor some duration. It should be understood that two distinct reactionsare simultaneously occurring at this point: Oxidation of SO₂→SO₃ and asubsequent reaction of the SO₃ thus formed with MgO to form MgSO₄.Typically, the reaction is allowed to continue until the sample issaturated (meaning all the possible MgO is reacted to form the sulfate)The second aspect of the TGA is to regenerate the sorbent. This isachieved through use of a lower temperature (typically 590° C.) and areducing atmosphere (typically H₂), so that the sorbent being studiedreleases the sorbed SO_(x) as H₂S. The TGA-SO_(x), plot for one cycle ofsuch a test on one of applicant's HTL compounds is shown in FIG. 13.

[0151] Methods for Forming HTL Compositions which are ParticularlyResistant to Mechanical Stress.

[0152] The HTL compounds of this invention can be formed into variousshapes (particles, microspheroidal particles, extrudates, pellets) whichare harder and more dense than HTL compounds made by prior artprocesses. These qualities make applicant's HTL compounds more usefulfor certain applications e.g., catalysts, sorbents in general (andSO_(x) sorbents in particular), ion exchange pellets (e.g., for watersofteners). If made according to the teachings of this patentdisclosure, such physical forms will display greater resistance to wear,attrition, or impact, as well as improvement (i.e., increase) in thebulk density of the HTL compounds formed by applicant's methods.

[0153] The following Table IV summarizes improvements in two physicalproperties (i.e., attrition index and apparent bulk density (“ABD”)) forvarious samples that were spray dried into particle forms and activatedaccording to the teachings of this patent disclosure. This activationmethod would also be applicable to other physical forms of such HTLcompounds, e.g., extrudates, pellets or beads. TABLE IV Attrition IndexHTL Composition (ASTM) *ABD (g/cc) 2 Mg/1Al (Step 1 Activation) 3.9 0.392 Mg/1Al (Step 2 Activation) 0.54 0.96 5 Mg/1Al (Step 1 Activation) 150.36 5 Mg/1Al (Step 2 Activation) 0.65 0.75

[0154] The 2Mg/1Al sample described in Table IV also was subjected to anadditional heat treatment step at 732° C./1 hr. This additional heattreatment has been described as an optional, “Step 3” in previous partsof this patent disclosure. This additional heating was performed to showthat applicant's “activation” was of irreversible nature, meaning thephysical properties do not revert to the original activation values.Therefore, applicant considers the products of this “activation” to benew compositions of matter. In any case, the results of this Step 3process are shown in Table V. TABLE V Attrition Index HTL Composition(ASTM) ABD (g/cc) 2 Mg/1Al (Step 1 Activation) 3.9 0.96 2 Mg/1Al (Step 2Activation) 0.54 0.96 2 Mg/1Al (Additional heat to 0.81 0.80 732 C./1hr.)

[0155] Applicability of Activation Process toward HTL Compounds whichCrystallize with HTL Structure during Slurry Synthesis.

[0156] The aforementioned activation process (i.e., heat treatmentfollowed by hydration) can be applied to HTL compounds that are used asstarting materials in the second embodiment of applicant's invention.That is to say that a HTL compound can be heat treated to form a“collapsed” or “metastable” material that can be rehydrated in the samemanner that the heat treated material of the first embodiment ofapplicant's invention was hydrated. If so heat treated, the hydrationprocess of the second embodiment of this invention will result information of a HTL phase. Here again, applicant's activation processimproves the physical characteristics of the HTL materials produced bysaid process. Again, these improvements include, but are not limited to,improved mechanical strength and density of the formed shapes (e.g., FCCparticles, fixed bed pellets, anion exchange beads, etc.) relative tocomparable compounds that do not experience applicant's activationprocess. It also should be noted that, for those materials which formHTL compounds from HTL starting materials (i.e., the second embodimentof applicant's invention), the resulting ETL phase may or may not beexactly identical to the starting HTL phase (in terms of exact identityof peak position and intensity), but which will nonetheless displayclearly identifiable HTL compound peaks and possess the above-notedimproved physical characteristics.

[0157] To show this advance, an example is given of a HTL containingSO_(x) sorbent (marketed by Akzo Nobel under the trade name “KDESOX®”)that was subjected to applicant's activation process. The followingTABLE VI summarizes the physical characteristics of the HTL-containingcomposition, before and after Applicant's activation process. TABLE VIKDESOX KDESOX HTL Composition (as received) “Activated” Attrition Index,ASTM 1.8 0.77 Bulk Density, g/cc 0.81 0.97

[0158] Thus, the physical properties (shown here as attrition index andbulk density) of a commercial available HTL compound made into FCCparticles can be improved markedly by subjecting them to applicant'sActivation process.

[0159] While this invention has been described with respect to varioustheories, specific examples and a spirit which is committed to theconcept of the use of an “activation process” that is based upon heattreatment and hydration of collapsed, HTL-forming, compounds, the fullscope of this invention relates to such activation of anionic clays ingeneral; hence the full scope of this invention should be regarded asbeing limited only by the claims that follow.

What is claimed is:
 1. A solid solution comprising magnesium andaluminum in a ratio of 2:1 to 5:1 and having an X-ray diffractionpattern displaying at least a reflection at a two theta peak position atabout 43 degrees and about 62 degrees; wherein the compound is notderived from a hydrotalcite like compound.
 2. The solid solution ofclaim 1, wherein the magnesium and aluminum are in a ratio of 2:1 to 4:13. The solid solution of claim 1, wherein the source of magnesium ismagnesium hydroxy acetate, magnesium acetate, magnesium hydroxide,magnesium nitrate, magnesium carbonate, magnesium formate, magensiumchloride, magnesium aluminate, hydrous magnesium silicate, magnesiumcalcium silicate, or a mixture of two or more thereof.
 4. The solidsolution of claim 1, wherein the source of aluminum is alumina sol,alumina gel, crystalline alumina, aluminum acetate, aluminum nitrate,aluminum hydroxide, aluminum carbonate, aluminum formate, aluminumchloride, hydrous aluminum silicate, aluminum calcium silicate, or amixture of two or more thereof.
 5. A method for decreasing SO_(x)emissions from a fluid catalytic cracking unit comprising adding thesolid solution of claim 1 to the fluid catalytic cracking unit to reducethe SO_(x) emissions.
 6. A composition comprising the solid solution ofclaim 1 and at least one SO₂→SO₃ oxidation catalyst comprised of a metalselected from the group consisting of cerium, vanadium, platinum,palladium, rhodium, molybdenum, tungsten, copper, chromium, nickel,iridium, manganese, cobalt, iron, ytterbium and uranium.
 7. Acomposition comprising the solid solution of claim 1 and at least oneSO₂→SO₃ oxidation catalyst comprised of a metal selected from the groupconsisting of cerium and vanadium.
 8. A method for decreasing SO_(x)emissions from a fluid catalytic cracking unit comprising adding acompound of formula (II) to the fluid catalytic cracking unit to reducethe SO^(x) emissions; wherein the compound of formula (II) is:(Mg_(m)Al_(n)(OH)_(2m+2n))OH_(n).bH₂O  (II) wherein b is between 0 and10; and m and n are selected so that the ratio of m/n is about 1 toabout
 10. 9. The method of claim 8, wherein the ratio of m/n is from 2to
 5. 10. The method of claim 8, wherein the ratio of m/n is from 2 to4.
 11. The method of claim 8, wherein the compound of formula (II) isMg₆Al₂(OH)₁₈.4.5H₂O.
 12. The method of claim 8, wherein the compound offormula (II) is collapsed.
 13. A method for decreasing SO^(x) emissionsfrom a fluid catalytic cracking unit which comprises adding acomposition comprising a compound of formula (II) and one or moreSO₂→SO₃ oxidation catalysts comprised of a metal selected from the groupconsisting of cerium, vanadium, cobalt, copper, platinum, palladium,rhodium, iridium, molybdenum, tungsten, chromium, nickel, manganese,iron, ytterbium and uranium, to the fluid catalytic cracking unit toreduce the SO_(x) emissions; wherein the compound of formula (II) is:(Mg_(m)Al_(n)(OH)_(2m+2n))OH_(n).bH₂O  (II) wherein b is between 0 and10; and m and n are selected so that the ratio of n/n is about 1 toabout
 10. 14. The method of claim 13, wherein the ratio of m/n is from 2to
 5. 15. The method of claim 13, wherein the ratio of m/n is from 2 to4.
 16. The method of claim 13, wherein the compound of formula (II) isMg₆Al₂(OH)₁₈.4.5H₂O.
 17. The method of claim 13, wherein the compound offormula (II) is collapsed.
 18. The method of claim 13, wherein thecomposition comprises a compound of formula (II) and one or more SO₂→SO₃oxidation catalysts comprised of a metal selected from the groupconsisting of cerium and vanadium.
 19. A method for decreasing SO_(x)emissions from a fluid catalytic cracking unit comprising adding ahydrotalcite like compound having an XRD pattern which has 2 theta peakpositions that reasonably resemble those found in ICDD card 35-965 tothe fluid catalytic cracking unit to reduce the SO_(x) emissions.
 20. Amethod for decreasing SO_(x) emissions from a fluid catalytic crackingunit comprising adding a composition comprising a hydrotalcite likecompound having an XRD pattern which has 2 theta peak positions thatreasonably resemble those found in ICDD card 35-965 and one or moreSO₂→SO₃ oxidation catalysts comprised of a metal selected from the groupconsisting of cerium, vanadium, cobalt, copper, platinum, palladium,rhodium, iridium, molybdenum, tungsten, chromium, nickel, manganese,iron, ytterbium and uranium to the fluid catalytic cracking unit toreduce the SO_(x) emissions.
 21. The method of claim 20, wherein thecomposition comprises a hydrotalcite like compound having an XRD patternwhich has 2 theta peak positions that reasonably resemble those found inICDD card 35-965 and one or more SO₂→SO₃ oxidation catalysts comprisedof a metal selected from the group consisting of cerium and vanadium.